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27 Cards in this Set

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Definition of magnification

the number of times an image appears larger compared to the actual size of the object

What formula is used to calculate Magnification?

The triangle is Observed size/ Actual size X Magnification

Convert:


Centimeter (cm)


Millimeter (mm) to


Micrometer (um) to


Nanometer (nm)

Centimeter X 1000 to


Milimeter X 1000 to


Micrometer X 1000 to


Nanometer


Definition of resolution

the ability to distinguish between two different points

Best resolution of a light microscope

0.2 micrometres

Best magnification of a light microscope

x1500

What are Light microscope mainly used to look at?

To look at whole cells or tissues

How does a light microscope work?

> They use light and several lenses in order to magnify.> Specimens are illuminated with light which is focused using glass lenses

Advantages of a light microscope

> Cheap


> Easy to use


> Can examine living things

Disadvantages of a light microscope

> Specimens have to be small, thin and transparent


> Have a low resolution due to light

How does a confocal scanning microscope work?

> They use laser lights to scan a specimen thats usually tagged with fluorescent dyes.


> The laser beam which is focused through a lens is aimed at a beam splitter


> This splits the beam and some of the light to the specimen


> When the laser hits the dyes it causes them to give off fluorescent light


>This light is then focused through a pinhole onto a detector which is hooked up to a computer, which generates an image.




overall use laser light to scan an object point by point and assemble, by computer, the pixel information into one image

What does a pinhole for laser scanning microscope do?

The pinhole means that any out-of-focus light is blocked, so these microscopes produce a much clearer image

Advantages of a confocal scanning microscope

> Builds a clean 3d image


> Can look at objects at different depths in thick specimens


> Images are high resolution

Disadvantages of a confocal scanning microscope

> Quite big


> Doesn't always show full sample

Best resolution of a confocal scanning microscope

20 nanometres

Best magnification of a confocal scanning microscope

x1500

How does a TEM Microscope work?

> They use elctromagnets to focus a beam of electrons which is then transmitted through the specimen to produce a 2D image.


> Denser parts of the specimen absorb more elections, which makes them look darker on the image.

Advantages of TEM

> Can look at small organelles


> High resolution

Disadvantages of TEM

> Can only be used on thin specimens


> Angles at which the specimen is cut can affect how they appear


> Specimen are dead as they must be viewed in a vacuum

Best resolution of TEM

0.0002 micrometres or 0.2 nm

Best magnification of TEM

more than 1,000,000

How does a SEM work?

They scan a beam of electrons across the specimens. This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.

Advantages of a SEM

produces a 3D image

Disadvantage of SEM

> Have a lower resolution than TEMs


> Specimens are dead as they must be viewed in a vacuum


> Only shows the surface of cells

Best resolution of SEM

0.002 micrometres

Best magnification of SEM

less than 500,000

Similarities of SEM & TEM

> Both are large and very expensive


> Need a great deal of skills and trainning to use